Analysis of cells and analytes in fluid samples, particularly bodily fluid samples, often provides critical diagnostic and treatment information for physicians and patients. Immunoassays utilize the specificity of the antigen (Ag)—antibody (Ab) reaction to detect an Ag or Ab in a sample. In solid phase immunoassays, one reagent (e.g., the Ag or Ab) is attached to a solid surface, facilitating separation of bound reagents or analytes from free reagents or analytes. The solid phase is exposed to a sample containing the analyte, which binds to its Ag or Ab; the presence of this binding is indicative of the presence of the analyte in the sample, and extent of this binding can be quantitated to provide a measure of the analyte concentration in the sample. Transduction of the binding event into a measurable signal, however, is affected by a number of limitations, including constraints of particle movement on the solid phase and background signal, which affect the specificity and applicability of immunoassays. In addition, related analytes of interest may compete or otherwise interfere with one another in an assay, rendering it difficult to assess correctly the presence of more than one analyte of interest.